Various types of microphones have been used in consumer electronics, including condenser microphones and MEMS microphones. In addition, tilt or orientation sensors have recently seen various implementations in consumer electronic devices. These tilt sensors are capacitive devices which are low resolution accelerometers that respond to the force of gravity.
Accelerometers used as tilt or orientation sensors in the prior art have typically been surface micromachined MicroElectroMechanical System (MEMS) devices comprising thick layers of polysilicon, typically on the order of several microns, to form the inertial or moving mass member and associated electrodes. These types of designs are not generally compatible with the requirements for making a microphone, which requires a very sensitive membrane, typically with a thickness of 1 micron or less.
A capacitive microphone such as that disclosed in U.S. Pat. No. 6,535,460 to Loeppert et al (hereafter referred to as the '460 patent) discloses a diaphragm member typically made of polysilicon and a perforated backplate member which is a sandwich of polysilicon and silicon nitride layers. Integrating an accelerometer with a microphone such as that described in the '460 patent requires using the above-mentioned layers which comprise the microphone to create a capacitive structure that responds to gravity. Given the above-described structural incompatibility of accelerometer and microphone designs, this integration is not easily achieved.
It is an object of this invention to integrate at least one microphone and at least one orientation sensor together on a common substrate while satisfying the structural and functional requirements of both applications.
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